Thought I'd throw a few in to the pot for now. Not all exactly the heaviest ever or owt - some just sound it in the context of the song they're in, the way they punctuate the space or in their tone somehow.

I'm glad that 'The Thing that Should Not Be' is mentioned

I've not heard 'To Carry The Load' by Crowbar before (or any Crowbar really, except their cover of No Quarter), but yeah, sounds bloody great. More like what I'd consider to be 'heavy', whatever that is. Listening to a Crowbar mix on youtube now - they certainly have weight